Method and apparatus for localized liquid treatment of the surface of a substrate

ABSTRACT

A method and apparatus for dispensing a liquid on the surface of a localized zone of a substrate, for example for cleaning of etching purposes. Along with the liquid, a gaseous tensio-active substance is supplied, which is miscible with said liquid and when mixed with the liquid, reduces the surface tension of said liquid, thus containing the liquid in a local zone of the substrate surface.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 09/159,801 filed on Sep. 23, 1998 and claims priority benefitsunder 35 U.S.C. §119(e) to United States provisional application SerialNo. 60/059,929, filed on Sep. 24, 1997 and claims benefit of No.60/079,688, filed on Mar. 27, 1998 and claims benefit of No. 60/084,651,filed on May 6, 1998.

FIELD OF THE INVENTION

The present invention is related to a method of localized liquidtreatment of the surface of a substrate, like cleaning or etching. Theinvention is also related to an apparatus used to perform saidtreatment. Application of the invention is possible in a number of wetprocessing steps which are frequently used, e.g. in the fabrication ofintegrated circuits or liquid crystal displays.

BACKGROUND OF THE INVENTION

In the fabrication of micro-electronic devices such as integratedcircuits or liquid crystal displays, a substrate has to go through anumber of fabrication steps, including wet etching, wet cleaning orrinsing.

In the documents U.S. Pat. No. 5,271,774 and Japanese PatentJP-A-07211686, methods are described to remove a liquid from the surfaceof a substrate by applying a gaseous substance to the substrate, which,when mixed with the liquid, reduces the surface tension of the liquid,so that it can be easily removed from the surface by a centrifugalforce, i.e. by subjecting the substrate to a rotary movement. However,these methods are only applicable to the substrate a whole, and cannotbe used for local treatment of the substrate. Document EP-A-817246 isdescribing an apparatus and method for wet cleaning or etching of flatsubstrate surfaces, whereby a substrate is moved through a stationaryamount of liquid. This method is also related to a treatment of thesubstrate as a whole, not of a local zone of said substrate.

During some processing steps, an annular edge area of the substrate istreated, for example for the removal of certain layers, like a resist ora metal film (e.g. Cu). Sometimes, it is only the outer rim of thesubstrate which is treated, while the top and bottom surfaces of thesubstrate must remain untouched.

Techniques exist whereby a beam of liquid is directed to the edge areaor the rim of a rotating substrate in order to perform these processsteps. However these existing techniques offer a poor protection of thesubstrate surface against the cleaning liquid. It would therefore beadvantageous to find a way of protecting the substrate surface whiletreating said annular edge area or its outer rim with a liquid. Anotherdisadvantage of existing techniques is that the rotational speed of thesubstrate during processing must be relatively high, which isparticularly problematic for large substrates.

Some processing steps require the removal of larger sized features fromthe substrate surface, e.g. for revealing underlying zero markers, whichare used for the accurate lateral positioning during processing, e.g.,during photographic exposure. Although the definition of the zeromarkers themselves requires high accuracy, the accuracy requirements ofthe window for removing a layer on top of the zero markers can be fairlyrelaxed. So far in the state of the art, the use of a photo resist stepis mostly used to accomplish these areas. By using a photo resist step,a patterned protective resist layer is obtained on the substratesurface. The pattern is such that the areas to be etched are not coveredwith resist. After this, the substrate is etched and the photo resistlayer is removed. This is however an expensive and time-consumingeffort.

An alternative way of producing such larger sized areas which are freeof film, consists of a local shielding by shielding plates during filmdeposition. However, this technique leads to an increased risk ofparticle contamination and scratch formation on the substrate.Furthermore, this shielding technique is not generally applicable. Itrequires compatibility of the shielding plates with the depositionprocess of interest. To produce these larger sized features, it wouldtherefore be advantageous to find a method that allows less accuracy butlower cost and higher processing speed, without creating any particlecontamination.

Document JP-A-11166882 describes a pre-concentration or collectiontechnique, used in contamination measurements for semi-conductors. It isa technique, whereby a droplet is moved over the substrate surface, inorder to collect contaminants and subsequently analyze theirconcentrations. Currently, this technique is mainly used on siliconsurfaces, by rendering the surface hydrophobic by way of anHF-treatment. This way, the water-based droplet is contained. Thetechnique is however not confined to silicon surfaces. In some cases, ithas been observed that the contact angle between the droplet and thesubstrate surface is insufficient. Furthermore, it would be advantageousto find a method whereby, in the case of silicon surfaces, the extraprocessing step of providing an HF-treatment would become unnecessary.

Document U.S. Pat. No. 5,492,566 describes a way of holding a substrateto a flat surface by way of the Bernoulli effect. By supplying a gas ata high speed between said substrate and said surface through an annularnozzle, a pressure drop will result, under said substrate, thus holdingsaid substrate to said surface. Substrates held in this way can besubjected to various wet treatment steps, like cleaning or etching.However, a danger exists of liquid attaching itself to the rim or thebackside of the substrate.

SUMMARY OF THE INVENTION

The present invention relates to a method of dispensing liquid on a partof a substrate for processing of the substrate, e.g. for cleaning oretching purposes, while another part of said substrate is prevented fromcontacting said liquid, said method comprising the steps of:

supplying a liquid on a part of said substrate; and

simultaneously with said step of supplying a liquid, supplying a gaseoustensio-active substance to a surface, said gaseous substance being atleast partially miscible with said liquid and when mixed with saidliquid yielding a mixture having a surface tension lower than that ofsaid liquid.

A first embodiment of the invention is a method wherein said substrateis circular shaped,

wherein the step of supplying a liquid on a part of said substrateincludes supplying at least one stream of a liquid so that said streamhits a flat surface of said substrate in an area of said surface, saidarea being adjacent to an outer rim of said substrate,

wherein the step of supplying a gaseous tensio-active substance to saidsurface includes supplying at least one stream of a gaseoustensio-active substance to the flat surface of said substrate so thatsaid stream hits said surface in an area which is adjacent to the areahit by said liquid stream, and closer to the center of rotation, and

further comprising the step of:

rotating the circular shaped substrate about an axis of rotation,preferably in a horizontal plane, the axis being perpendicular to thesubstrate surface and through a center of gravity said substrate.

An additional stream of liquid may be supplied to the opposite surfaceof said substrate, in order to treat the whole of said opposite surface.

According to another embodiment of the invention, a stream of liquid maybe directed at the outer rim of the substrate, while the flat surfacesare protected from said liquid by a stream of a gaseous tensio-activesubstance.

Another embodiment of the invention is a method wherein the substrate iscircular shaped and has two sides, a first side consisting of an annularedge area and a central area,

the method further comprising the step of holding the circular shapedsubstrate,

wherein the step of supplying a liquid on a part of said substrateincludes supplying a stream of liquid to the entire annular edge area ofthe first side of the substrate, and

wherein the step of supplying a stream of a gaseous tensio-activesubstance includes supplying a stream of a gaseous tensio-activesubstance to the central area of the surface.

In this method, the substrate may be subjected to a rotational movement,the axis of rotation being perpendicular to the substrate surface andcomprising the center of said substrate.

An additional stream of liquid may be supplied to a surface which isopposite to a surface of which the annular edge area is treated, inorder to treat the whole of said opposite surface.

Another embodiment of the present invention is a method wherein a iscircular shaped, wherein the step of supplying a gaseous tensio-activesubstance to said surface includes supplying streams of a gaseoustensio-active substance to border areas between said amount of liquidand said flat surfaces, and

further comprising the steps of:

holding the circular shaped substrate, and

providing a means of bringing an annular edge area of both flat surfacesof said substrate, and the outer rim of said substrate into contact withan amount of liquid.

In this method, the substrate may be subjected to a rotational movement,the axis of rotation being perpendicular to the substrate surface andcomprising the center of said substrate.

Another embodiment of the present invention is a method, wherein thesubstrate has two sides, a first side and a second side,

further comprising the step of placing the second side of the substrateon a flat, rotating surface, said rotating surface containing an annularchannel, so that said second side of said substrate is covering saidchannel,

wherein said step of supplying a gaseous tensio-active substanceincludes supplying a stream of gaseous tensio-active substance throughsaid annular channel and in the direction of said substrate, so thatsaid substrate is held on said rotating surface by a Bernoulli effect,and

wherein said step of supplying a liquid on a part of said substrateincludes supplying a stream of the liquid on the first side of saidsubstrate.

Another embodiment of the present invention is a method, wherein thesubstrate has a first side and a second side,

wherein the step of supplying a liquid on a part of said substrateincludes supplying, through a first channel, a continuous stream ofliquid to a part of the first side of the substrate which is preferablyhorizontally placed,

further comprising the step of draining said stream of liquid from saidfirst side through a second channel, the second channel beingconcentrically placed around the first channel,

and wherein the step of supplying a gaseous tensio-active substanceincludes supplying to said first side a stream of a gaseoustensio-active substance around said second channel, to prevent remainderliquid from making contact with the first side of the substrate which isnot contained within the second channel. In this embodiment, the gaseoustensio-active substance may be drained from the substrate surfacethrough an additional channel.

Another embodiment of the present invention is a method, wherein thestep of supplying a liquid on a part of said substrate includes bringingan amount of liquid into contact with a part of a flat surface which ispreferably horizontally placed, and

wherein the step of supplying a gaseous tensio-active substance to saidsurface includes supplying to said surface a stream of gaseoustensio-active substance around said amount of liquid, thereby preventingsaid liquid from making contact with the rest of said surface. In thisembodiment, the gaseous tensio-active substance may be drained from thesubstrate surface through an additional channel.

The present invention is also related to an apparatus for subjecting asubstrate to a localized liquid treatment for cleaning or etching of thesubstrate, said apparatus comprising means for holding said substrate, afirst supply system adapted to supply a liquid on a first part of thesurface of said substrate, and a second supply system adapted to supplya gaseous substance to a second part of said substrate, the second partof the substrate adjacent to the first part which is treated by saidliquid.

In such an apparatus, a means may be provided for rotating saidsubstrate around an axis which is perpendicular to said substrate andwhich comprises the center of said substrate.

According to one embodiment, an apparatus is proposed for treating anannular edge area of at least one flat surface of a circular shaped,preferably horizontally placed substrate, comprising at least one fixedpair of nozzles, a nozzle being defined as an apparatus able to supply acontiguous stream of liquid. Of this pair, one nozzle is used to supplya stream of liquid on said annular edge area, while the other is used todispense a gaseous tensio-active substance on an area of said flatsurface adjacent to said annular edge area, and closer to the center ofsaid substrate.

Said pair of nozzles may be positionable on any location along a fixedradius of said substrate. A nozzle may be added on one of the flatsurfaces of said substrate which is opposite to a surface of which theedge area is treated, said nozzle being used to dispense a stream ofliquid on the whole of said opposite surface.

According to another embodiment, an apparatus is provided for treatingan annular edge area of a flat surface of a circular shaped substrate,the apparatus having a first supply system and a second supply system,

wherein the substrate has a geometric center, an axis which isperpendicular to said substrate at the geometric center of saidsubstrate, a central part around the axis of the substrate and anannular edge,

wherein said first supply system includes a first annular channeladapted to supply the liquid to the entire annular edge area of thesurface of said substrate,

wherein said second supply system includes a central channel adapted tosupply a gaseous substance to the central part of said substrate, thecentral channel being coaxial with the axis of the substrate, and

wherein said second supply system further includes a second annularchannel placed concentrically with respect to the first channel andcloser to the geometric center of said substrate, said second channeladapted to guide the gaseous substance coming from the central part ofsaid substrate, in order to prevent said liquid from touching saidcentral part.

Said apparatus may rotate around an axis which is perpendicular to saidsubstrate and which comprises the center of said substrate. A nozzle maybe added on one of the flat surfaces of said substrate which is oppositeto a surface of which the edge area is treated, said nozzle being usedto dispense a stream of liquid on the whole of said opposite surface.

A sealing device may be added between said substrate and the outer wallof said second annular channel.

According to another embodiment, an apparatus is proposed for treatingan annular edge area of both flat surfaces and the outer rim of acircular shaped substrate, placed preferably in a horizontal plane,comprising:

means for holding said substrate,

a first supply system adapted to supply a liquid on a first part of thesurface of said substrate,

a second supply system adapted to supply a gaseous substance to a secondpart of said substrate,

a container filled with an amount of treatment liquid so that a pressureis maintained above the surface of said amount of treatment liquid, saidpressure being less than or equal to an ambient pressure, said containerhaving a narrow gap in one side, into which said circular substrate ispartially inserted, so that at least a portion of said annular edge andsaid outer rim of said substrate is immersed in said liquid, and

at least one pair of nozzles, one nozzle of said pair on each side ofsaid substrate, directing a stream of a gaseous substance at a borderarea between said container and said substrate.

Said apparatus may rotate around an axis which is perpendicular to saidsubstrate and which comprises the center of said substrate.

According to another embodiment, an apparatus is proposed for treating alocal zone of a preferably horizontally placed substrate, said apparatuscomprising

a first supply system including a central channel used to supply astream of liquid to the surface of said substrate and a second channel,concentrically surrounding the first channel, and draining said streamof liquid from the surface of said substrate; and

a second supply system including a third channel, concentricallysurrounding the second channel and used to supply a stream of atensio-active substance to the substrate surface.

According to the same embodiment, a fourth channel may be concentricallyplaced with respect to said third channel, said fourth channel beingused to drain said gaseous tensio-active substance from the substratesurface.

A sealing device may be added between said substrate and the outer wallof said second channel. In case of a fourth channel, an additionalsealing device may be placed between said substrate and the outer wallof the apparatus.

According to another embodiment, an apparatus is proposed for treating alocal zone or for collecting impurities from the surface of a preferablyhorizontally placed substrate, said apparatus comprising:

a first supply system including a central channel, the central channelcontaining an amount of a liquid such that said liquid is in contactwith the surface of said substrate, and that a pressure is maintainedabove a surface of said amount of liquid, said pressure being less thanor equal to an ambient pressure on the substrate surface, and

a second supply system including a second channel, the second channelconcentrically surrounding the central channel, and supplying a streamof a gaseous tensio-active substance on the surface of said substrate.

According to the same embodiment, a third channel may be placedconcentrically with respect to said second channel, said third channelbeing used to drain said gaseous tensio-active substance from thesubstrate surface.

A sealing device may be added between said substrate and the outer wallof said central channel. In case of a third channel, an additionalsealing device may be placed between the substrate and the outer wall ofthe apparatus.

An object of the present invention is to provide a method and apparatusto perform a liquid treatment of a part of a substrate, such as acleaning or etching step, while another part of said substrate isprotected from said liquid by the use of a gaseous substance.

SHORT DESCRIPTION OF THE DRAWINGS

FIG. 1a (front and top view) describes the method and apparatusaccording to a first embodiment of the invention, used to clean or etchan edge area of a rotating substrate.

FIG. 1b (front view) describes a method and an apparatus for treatingthe outer rim of a rotating substrate.

FIG. 1c (front view) describes the method and an apparatus according tothe invention for performing a backside cleaning.

FIG. 2 (front and top sectioned view) describes a second method andapparatus according to the invention, used to clean or etch an annularedge area of a substrate.

FIG. 3a (sectioned front view and top view) describes a third method andan apparatus according to the invention, used to clean or etch anannular edge area and the outer rim of the substrate.

FIG. 3b (sectioned front view and top view) represents an alternativeform of the apparatus shown in FIG. 3a.

FIG. 4 (front view) describes the method according to the invention,used to hold a substrate by way of the Bernoulli effect.

FIGS. 5a and b (front and top sectioned view) describes the method andan apparatus according to the invention, used to clean or etch a localarea of a substrate by applying a continuous stream of a liquid.

FIGS. 6a and b (front and top sectioned view) describes the method andapparatus according to the invention, used to contain a small amount ofa liquid on a part of the surface of the substrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The presently preferred embodiments of the invention will now bedescribed by reference to the accompanying figures, wherein likeelements are referred to by like numerals. FIG. 1a describes the methodand apparatus according to a first embodiment of the invention, wherebya liquid, used for cleaning or etching, is supplied on a horizontallyplaced rotating circular shaped substrate 1 through a first nozzle 2,while a gaseous tensio-active substance is supplied through a secondnozzle 3. The rotation of the substrate is indicated by the arrow. Therotation in this and all following embodiments (if a rotation isapplied) is occurring around the axis perpendicular to the substrate andcomprising the center of said substrate.

In the apparatus of FIG. 1a, both nozzles are placed such that thestreams of liquid and tensio-active substance hit the substrate surfaceon two spots which are preferably lying along a radius of saidsubstrate. The spot where the liquid stream hits the surface is lying onan annular edge area 4, the spot where the stream of tensio-active gashits the surface is lying next to the first spot and closer to thecenter of the substrate. Both nozzles are fixed. The liquid, suppliedthrough nozzle 2 can be used to clean or etch a well defined annularedge area 4 of the surface of the substrate, while the rest of saidsurface is protected from making contact with tho liquid, by the gaseoustensio-active substance. This substance, when mixed with the liquid,reduces the surface tension of said liquid, so that it does not spreadout over said surface, but becomes contained and is easily removed fromtide surface by the centrifugal forces, resulting from the substrate'srotational movement. The walls 5 of the compartment in which thesubstrate is placed are slanted, so that they can provide an efficientremoval of liquid droplets 6, without splashing onto the substrate. Theliquid may be selected from the group consisting of an etching liquid, acleaning liquid and a rinsing liquid. The cleaning liquid may beselected from the group consisting of a mixture of NH₄OH. H₂O₂, and H₂O;a mixture of HCL, H₂O₂ and H₂O; diluted HCL; and a mixture comprisingO₃. The rinsing liquid may be selected from the group consisting of H₂O;and a mixture of H₂O and an acid, the acid mixture having a pH between 2and 6.

The angles between the nozzles and the substrate surface may differ fromthe exemplary case of FIG. 1a. It is beneficial for the liquid nozzle tobe placed at an angle which minimizes splashing. Both nozzles may beplaced on a movable structure, so that they can be fixed at a variableposition along the radius of said substrate. Several pairs of nozzles(2,3) may be placed on fixed positions on one or both sides of thesubstrate.

This embodiment represents an improvement on the state of the art inthat it allows the treatment of a localized edge area of the substratesurface, without contacting the central part of said substrate. Anadditional advantage of the method according to the invention is that itallows a rotational movement of the substrate at a lower speed, comparedto existing methods.

If said nozzles are directed at the outer rim 7 of the substrate, as inFIG. 1b, the method according to the invention is suitable for thetreatment of the rim, whereby the surface of the substrate is protectedfrom the liquid. A second pair of nozzles 8 (liquid) and 9 (gaseoustensio-active substance) may be added on the opposite side of thesubstrate, to improve the efficiency of the rim treatment process.

An additional nozzle 10 may be added on the opposite side of thesubstrate, as is shown in FIG. 1c. This setup is then suitable for theprocess of backside cleaning or etching, in which the backside 11 of thesubstrate is treated as well as a limited area 12 of the front side, andthe outer rim 7. Using the method of invention, the central part 13 ofthe front side of the substrate can be effectively shielded from thetreatment liquid.

FIG. 2 describes the method and apparatus according to anotherembodiment of the invention, in which a liquid is dispensed on anannular edge area 20 of a circular shaped substrate 1. The substrate maybe stationary or rotating. An apparatus 19 is placed above the surfaceof the substrate, consisting of two concentric annular channels 21 and22. Said apparatus may also be rotating around the central perpendicularaxis of the substrate. Through the outer channel 21, a liquid issupplied on the edge of the rotating substrate. At the same time agaseous substance which is preferably tensio-active, is supplied on thecentral part of the substrate, through a central nozzle 23. The gaseoustensio-active substance is flowing outward from the center of thesubstrate to the edge, where it is guided through the inner concentricchannel 22. Said gaseous substance reduces the surface tension of theliquid in such a way that the liquid is prevented from making contactwith the central part of said surface. In case the substrate isrotating, the centrifugal forces acting on the liquid will furtherfacilitate the removal of the liquid from the surface.

This embodiment allows also to treat an edge area of the substrate,presenting the added advantage that the liquid can be applied to thewhole of the edge area, which is also protected as a whole by thecentrally supplied gaseous tensio-active substance. The same structuremay be placed on the opposite side of the substrate, in order to treatboth edge areas simultaneously. Also, in case one apparatus 19 isapplied, a nozzle may be directed at the opposite side, supplying liquidon said opposite side, analogous to the action of nozzle 10 in FIG. 1c.The distance between the apparatus 19 and the substrate surface must besufficiently small, to optimize the separation between the liquid andthe gas.

In case both the apparatus 19 and the substrate 1 are stationary orrotating at the same speed, a sealing device, e.g. an O-ring, may beplaced between the substrate and the outer wall of channel 22, toseparate the central part from the treated edge area.

FIG. 3a describes the method and apparatus according to anotherembodiment of the present invention, in which a substrate 1 is subjectedto a rotational movement. To one side of the substrate is a container30, containing a liquid 31, to be used for the treatment of the edgeareas 32 and the outer rim 33 of the substrate 1. The gap 34 is made sothat it can receive the rotating substrate's edge, with very smallclearances. The pressure inside said container 30 is preferably lowerthan or equal to the pressure outside said container. Nozzles (35, 36)are present on both sides of the substrate, supplying streams of agaseous substance which is preferably tensio-active, to the border areabetween the container and the substrate, thereby preventing the liquidfrom touching the central part of the substrate.

In one aspect of this embodiment, the container may be rotating aroundthe substrate's central perpendicular axis, at the same or a differentspeed as the substrate. In this manner, the centrifugal forces willcontribute to the efficient separation between the liquid and thecentral area of the substrate. Also, the substrate may be stationary,while the container is rotating.

The container may even be of an annular form, so that the whole of theedge area to be treated is immersed in the treatment liquid. Also inthis case, said annular-shaped container may rotate at a speed, equal toor different from the speed of said substrate. In this case also, thesubstrate may be stationary. If the container has an annular form, as isshown in FIG. 3b, it should consist of two parts: a bottom part 100 inwhich to place the substrate, and a top part 101 which is placed ontothe first part, after which the compartment between both parts is filledwith a treatment liquid, e.g. via at least one opening 102 so that thesubstrate's annular edge area is totally immersed in said liquid. Alongthe outer perimeter of both parts of said container, a suitable sealingdevice 103 should be provided between said parts so that no treatmentliquid can escape from the container. Annular shaped nozzles 104 may beused to supply an equal amount of the gaseous tensio-active substance tothe border areas between the container and the substrate.

This embodiment presents the added advantage that the edge areas of bothsides and the outer rim of the substrate can be treated simultaneously.

For holding a substrate and subjecting it to a rotational movement inone of the previous embodiments of the present invention, a planetarydrive system can be used. In such a system, a set of rotating groovedwheels located around the perimeter of the round substrate, hold anddirectly drive the substrate. This offers an efficient removal of edgebeads. Also, there is a free access to both sides of the substrate.Alternatively, a vacuum chuck may be used to hold the substrate.

FIG. 4 describes the method according to another embodiment of theinvention, in which a stream of a gaseous tensio-active substance isused to hold a substrate 1 by way of the Bernoulli effect. The substrate1 is placed on a flat rotating surface 40 in which an annular nozzle 41is provided. The rotation of said surface 40 is indicated by the arrow.Through this nozzle, a tensio-active gaseous substance is supplied at acertain speed. This speed is responsible for a pressure drop between thesubstrate and the flat surface, causing the substrate to be held to saidsurface. Supports 42 are mounted on the surface 40 to ensure that thesubstrate is kept in place.

A nozzle 43 is placed on the opposite side to the annular nozzle and isused to supply a stream of treatment liquid. This embodiment is suitablefor the process of thinning of the substrate, by applying an etchingfluid on one surface, while the opposite surface is effectivelyprotected by the tensio-active gas.

FIG. 5a describes the method and apparatus according to anotherembodiment of the invention, in which a continuous stream of liquid issupplied on the surface of the substrate 1. An apparatus is used,consisting of three concentric channels. The central channel 50 is usedto supply the liquid on the surface of the substrate. The surroundingchannel 51 is used to drain the liquid from said surface. The thirdchannel 52 is used to supply a gaseous tensio-active substance whichreduces the surface tension of the liquid so that it is contained on alocalized area of the surface. A sealing device, e.g. an O-ring 53, maybe added between the substrate and the outer wall of the liquid drainingchannel 51. In this case, the stream of gaseous tensio-active substancemakes sure that any liquid leaking through the seal is contained on thearea to be treated.

FIG. 5b reveals an additional fourth channel 54 surrounding channel 52,which may be placed in case the gaseous substance must be prevented fromtouching the rest of the substrate or from leaking out into theenvironment. The arrows indicate that the gaseous tensio-activesubstance is drained from the surface of the substrate through thisfourth channel. However, it is equally possible for the gas to besupplied through the fourth channel 54 and drained through the thirdchannel 52.

Whatever the direction of the stream of gaseous tensio-active substancein the apparatus of FIG. 5b, an additional sealing device 55 may beplaced between the substrate and the outer wall of the apparatus, inorder to prevent the gaseous substance from leaking into theenvironment. Specifically, if the third channel 52 is positioned in theoutermost portion of the device (the configuration is such that thefourth channel 54 is placed between the second channel 51 and the thirdchannel 52), a sealing device may be placed at the outermost portion ofthe third channel 52. Alternatively, if the fourth channel is placedoutside of the third channel such that the fourth channel is theoutermost portion of the device, a sealing device 55 may be placed forthe fourth channel. In this manner, the placement of the fourth channel(either between the second and third channel or outside of the thirdchannel) allows for the gas to be removed out of the system in twodifferent directions. And, a sealing device may be placed between thesubstrate and the outer wall of the last concentric channel in theapparatus.

The device containing the three or four channels may be designed so thatit covers the area to be treated exactly, or it may be made smaller andsubsequently be scanned over the area to be treated.

The device containing the three or four channels may advantageously beplaced under a horizontally placed substrate. In this way, a splashingof liquid on the substrate when removing the device may be avoided.

This embodiment can be used to clean local areas of the substratesurface, or to etch these areas, such as zero marker areas, withoutrequiring a photo-resist pattern or shielding plates. For the productionof such larger sized film-free areas, this method presents a quicker andcheaper way compared to the classic photo step method. Compared to themethod using shielding plates, the method according to the presentinvention eliminates the danger of particle contamination or scratchformation.

FIG. 6a describes the method and apparatus according to anotherembodiment of the invention, which is suitable for the technique ofimpurity collection. It may also be suitable for obtaining larger sizedfilm-free areas, like zero-markers. An amount of liquid 60 is put intocontact with the surface of the substrate 1 through a central channel61. This channel is closed off on the top side. Advantageously, thepressure inside the channel 63 is lower than the ambient pressure actingon the substrate surface. The lower the pressure above the liquid, thehigher the amount of liquid which can be contained. A channel 62 whichis placed around the channel 61 is used to supply a gaseoustensio-active substance, which reduces the surface tension of the liquidso that said liquid is contained on a localized area of the surface. Incase a droplet of said liquid is used, a reduction of the pressure abovesaid droplet is unnecessary. In this case, the central channel 61 may beopen on top.

A sealing device such as an O-ring 63 may be added between the substrateand the outer wall of the channel 61. In this case, the stream ofgaseous tensio-active substance would make sure that any liquid leakingthrough the seal is contained on the area to be treated.

In FIG. 6b, an additional channel 64 is added to the apparatus. Thisversion of the apparatus is preferred when the gaseous tensio-activesubstance must be prevented from touching the rest of the substrate orfrom leaking into the environment. The arrows indicate that the gaseoustensio-active substance is drained from the surface of the substratethrough this third channel 64. However, it is equally possible for thegas to be supplied through the third channel and drained through thesecond channel.

Whatever the direction of the stream of gaseous tensio-active substancein the apparatus of FIG. 6b, an additional sealing device 65 mayadvantageously be placed between the substrate and the outer wall of theapparatus, in order to prevent the gaseous substance from leaking intothe environment.

This embodiment represents an improvement compared to the existingtechniques described in the state of the art, as it is capable ofholding an amount of liquid, larger than a droplet, so that a largeramount of contaminants can be collected. In case a droplet is used, theflow of the gaseous tensio-active substance increases the contact anglebetween the droplet and the surface to be treated. Eventually, it mayrender the pre-treatment of the substrate surface of hydrophilicsubstrates unnecessary.

It is intended that the foregoing detailed description be regarded asillustrative rather than limiting and that it is understood that thefollowing claims, including all equivalents, are intended to define thescope of the invention.

What is claimed is:
 1. A method of dispensing liquid on a fist part of asubstrate for cleaning or etching of the substrate, while a second partof said substrate is inhibited from contacting said liquid, said methodcomprising the steps of: supplying a liquid on the first part of saidsubstrate; and simultaneously with said step of supplying a liquid,supplying a gaseous tensio-active substance to the second part of saidsubstrate adjacent to the first part, said gaseous substance being atleast partially miscible with said liquid and when mixed with saidliquid yielding a mixture having a surface tension lower than that ofsaid liquid thereby inhibiting the liquid from contacting said secondpart.
 2. A method according to claim 1, wherein said substrate iscircular shaped, wherein the step of supplying a liquid on a part ofsaid substrate includes supplying at least one stream of a liquid sothat said stream hits a flat surface of said substrate in an area ofsaid surface, said area being adjacent to an outer rim of saidsubstrate, wherein the step of supplying a gaseous tensio-activesubstance to said surface includes supplying at least one stream of agaseous tensio-active substance to the flat surface of said substrate sothat said stream hits said surface in an area which is adjacent to thearea hit by said liquid stream, and closer to the center of rotation,and further comprising the step of: rotating the circular shapedsubstrate about an axis of rotation, the axis being perpendicular to thesubstrate and through a center of gravity said substrate.
 3. A methodaccording to claim 2, wherein the rotational movement is in thehorizontal plane.
 4. A method according to claim 1, wherein saidsubstrate is circular shaped and further comprising the step of rotatingthe circular shaped substrate about an axis of rotation, the axis beingperpendicular to the substrate surface and through a center of gravityof said substrate, wherein the step of supplying a liquid on the firstpart of said substrate includes supplying at least one stream of theliquid so that said stream hits an outer rim of said substrate, andwherein the step of supplying a gaseous tensio-active substance to saidsecond part includes supplying at least one stream of a gaseoustensio-active substance to an edge area of a flat surface of said secondpart of said substrate, said area being adjacent to the area of the rimonto which said liquid stream is supplied.
 5. A method according toclaim 4, wherein the rotational movement is in the horizontal plane. 6.A method according to claim 2, wherein the substrate has two sides, afirst side which includes the outer rim area and a second side, andfurther comprising the step of: supplying an additional stream of liquidto at least a portion of the second side.
 7. A method according to claim6, wherein the step of supplying an additional stream of liquid includessupplying liquid to the entire second side.
 8. A method according toclaim 1, wherein the substrate is circular shaped and has two sides, afirst side consisting of an annular edge area and a central area,further comprising the step of holding the circular shaped substrate,wherein the step of supplying a liquid on the first part of saidsubstrate includes supplying a stream of liquid to the entire annularedge area of the first side of the substrate, and wherein the step ofsupplying a stream of a gaseous tensio-active substance includessupplying a stream of a gaseous tensio-active substance to the centralarea of the substrate.
 9. A method according to claim 8, furthercomprising the step of subjecting the substrate to a rotational movementwith an axis of rotation being perpendicular to the substrate andthrough a center of gravity of said substrate.
 10. A method according toclaim 8, wherein the substrate has two sides, a first side whichincludes the outer rim area and a second side, and further comprisingthe step of: supplying an additional stream of liquid the entire secondside.
 11. A method according to claim 1, wherein the substrate iscircular shaped and has two flat surfaces, wherein the step of supplyinga gaseous tensio-active substance to said second part includes supplyingstreams of a gaseous tensio-active substance to border areas betweensaid liquid and said flat surfaces, wherein said liquid is selected fromthe group consisting of an etching liquid, a cleaning liquid and arinsing liquid; and further comprising the steps of: holding thecircular shaped substrate, and providing a means of bringing an annularedge area of both flat surfaces of said substrate, and the outer rim ofsaid substrate into contact with an amount of liquid.
 12. A methodaccording to claim 11, wherein said etching liquid is a dilute aqueoussolution, wherein said cleaning liquid is selected from the groupconsisting of a mixture of NH₄OH, H₂O₂, and H₂O; a mixture of HCL, H₂O₂and H₂O; diluted HCL; and a mixture comprising O₃, and wherein saidrinsing liquid is selected from the group consisting of H₂O; and amixture of H₂O and an acid, said acid mixture having a pH between 2 and6.
 13. A method according to claim 11, wherein the step of holding thecircular shaped substrate includes holding the circular shaped substratein a horizontal plane.
 14. A method according to claim 11, furthercomprising the step of subjecting the substrate to a rotationalmovement, the axis of rotation being perpendicular to the substrate andthrough a center of said substrate.
 15. A method according to claim 1,wherein the substrate has two sides, a first side and a second side,further comprising the step of placing the second side of the substrateon a flat, rotating surface, said rotating surface containing an annularchannel, so that said second side of said substrate is covering saidchannel, wherein said step of supplying a gaseous tensio-activesubstance includes supplying a stream of gaseous tensio-active substancethrough said annular channel and in the direction of said substrate, sothat said substrate is held on said rotating surface by a Bernoullieffect, and wherein said step of supplying a liquid on a part of saidsubstrate includes supplying a stream of the liquid on the first side ofsaid substrate.
 16. A method according to claim 1, wherein the substratehas a first side and a second side, wherein the step of supplying aliquid on the first part of said substrate includes supplying, through afirst channel, a continuous stream of liquid to the first part of thefirst side of the substrate, further comprising the step of drainingsaid stream of liquid from said first side through a second channel, thesecond channel being concentrically placed around the first channel, andwherein the step of supplying a gaseous tensio-active substance includessupplying to said first side a stream of a gaseous tensio-activesubstance around said second channel, to prevent remainder liquid frommaking contact with the first side of the substrate which is notcontained within the second channel.
 17. The method according to claim16, wherein the substrate is placed in a horizontal position.
 18. Themethod according to claim 16, wherein the gaseous tensio-activesubstance is drained from said substrate through an additional channel.19. A method according to claim 1, wherein the step of supplying aliquid on the first part of said substrate includes bringing an amountof liquid into contact with a part of a flat surface, and wherein thestep of supplying a gaseous tensio-active substance to said second partincludes supplying to said second part a stream of gaseous tensio-activesubstance around said amount of liquid, thereby preventing said liquidfrom making contact with a remainder of said substrate.
 20. The methodaccording to claim 19 wherein the substrate is placed in a horizontalposition.
 21. The method according to claim 19, further comprising thestep of draining said gaseous tensio-active substance from the substratethrough an additional channel.